The present invention relates generally to flash memory cards, and particularly to methods and apparatus for high voltage insertion in flash memory cards.
Small removable mass storage devices, constructed in the form of flash memory cards, are well known in the art. Flash memory cards, also referred to simply as flash cards, generally comprise non-volatile flash memories, and have become increasingly popular for use with digital cameras, digital music players, smart cellular phones, laptops and handheld devices, such as, but not limited to, personal digital assistants (PDAs).
One well-known kind of flash card is the xe2x80x9cCompactFlash(trademark)xe2x80x9d card, which is particularly popular for use with digital cameras. CompactFlash was first introduced in 1994 by SanDisk Corporation. The size of a CompactFlash card is typically 43 mmxc3x9736 mmxc3x973.3 mm. The CompactFlash card typically has 50 pins, as opposed to a 68-pin PCMCIA Personal Computer Memory Card International Association) card, and is about one-fourth the volume of the PCMCIA card. Yet the CompactFlash card may provide complete PCMCIA functionality and compatibility. The CompactFlash card may support more than one voltage input, such as 3.3 and 5 volts. The CompactFlash card also includes an onboard card interface controller that may increase performance, particularly on devices that have slow processors.
Another type of flash memory card is the xe2x80x9cMemoryStick(trademark)xe2x80x9d made by Sony, which may be used with digital cameras for additional storage. It uses a 10-pin connector and uses a serial data transfer method to move the data. It typically operates at 2.7 V to 3.6 V, and has dimensions of about 21.5 mmxc3x9750 mmxc3x972.8 mm.
Another popular flash memory card is the MultiMediaCard (MMC) made by Siemens/SanDisk and also available from Infincon. The MMC is even smaller than the aforementioned cards, typically being the size of a postage stamp. For example, a 32 MB MultiMedia Card may measure 32 mmxc3x9724 mmxc3x971.2 mm, and weigh less than 1.5 g. It operates at 2.7 to 3.6 volts, and may be used with cellular phones, PDAs (Personal Digital Assistants), music players and electronic organizers. Smaller size MMCs are also available.
Yet another type of flash memory card is the Secure Digital (SD) card from SanDisk. SD cards are similar in shape to MMC cards, but thicker, such as about 2.1 mm thick.
Small flash memory cards, especially the MMC, are typically stored and carried in plastic or metal pouches or cases with pockets for slipping the cards therein.
Reference is now made to FIG. 1, which illustrates a typical flash memory card 10 that also includes a card interface controller 12, such as but not limited to, the CompactFlash card. Flash memory card 10 typically includes a plurality of pads, which may comprise a plurality of control pads 14 and a plurality of inlet/outlet (I/O) pads 16. The control pads 14 may be used to communicate control signals and data between controller 12 and a user device (not shown), such as but not limited to, digital cameras, music players, cellular phones, laptops and PDAs. The I/O pads 16 may be used to communicate other input and output data between controller 12 and the user device.
Flash memory card 10 may comprise one or more memories 18, such as but not limited to, electrically erasable, programmable read only memories (EEPROMs). The controller 12 may serve as the interface in communication between memory 18 and the user device. Memory 18 may typically support high voltage functionality, such as, programming and erasing. On the other hand, controller 12 is usually not manufactured with EEPROM or flash technology, but rather with less expensive and more suitable processes, such as but not limited to, CMOS (complementary metal oxide silicon) processes. Accordingly, controller 12 typically does not require, and moreover cannot tolerate, high voltage for its functionality (e.g., voltage levels above Vdd).
The conflict in voltage characteristics between controller 12 and memory 18 may pose a problem. It would be advantageous to insert high voltage to memory 18, because high voltage may enable faster programming and erasing, and may be important for other functionalities, such as debugging. There are many applications where high voltage may be easily supplied to the card 10, such as from a mains outlet. However, memory 18 communicates with control pads 14 and I/O pads 16 only through controller 12. Since controller 12 is typically a low voltage component, it may not tolerate high voltage insertion. Thus, the low voltage restriction of controller 12 may prevent inserting high voltage in memory 18.
The present invention seeks to provide an improved flash memory card, which enables high voltage insertion in memories of such cards. In one embodiment of the invention, a high voltage switch logic module may be in communication with a control pad, a controller and one or more memories of the flash memory card. The high voltage switch logic module may selectively route voltage from the control pad to the controller or the memory. If the voltage input to the control pad does not exceed a predefined level, e.g., Vdd, then the voltage may be routed to the controller. If the voltage input to the control pad exceeds the predefined level, then the voltage may be routed to the memory. In such a manner, high voltage may be inserted in the memory, while at the same time circumventing the low voltage controller. The controller is protected from high voltage insertion and there is no need to modify any of the pads that already exist in flash memory cards.
There is thus provided in accordance with an embodiment of the present invention a flash memory card comprising a controller, at least one control pad, at least one memory, and a high voltage switch logic module in communication with the at least one control pad, the controller and the at least one memory, the high voltage switch logic module being adapted to selectively route voltage from the at least one control pad to one of the controller and the at least one memory.
In accordance with an embodiment of the present invention the high voltage switch logic module comprises a mode of operation wherein if a voltage input to the at least one control pad does not exceed a predefined level, then the high voltage switch logic module routes voltage from the at least one control pad to the controller. The predefined level may be in a range between ground (0 V) and Vdd. Alternatively, the predefined level may be in a range between ground and a power supply voltage level of the controller. Still alternatively, the predefined level may be higher than a power supply voltage level of the controller.
Further in accordance with an embodiment of the present invention the voltage routed to the controller is in a voltage range between ground and a power supply voltage level of the controller.
Still further in accordance with an embodiment of the present invention the high voltage switch logic module comprises a mode of operation wherein if a voltage input to the at least one control pad exceeds a predefined level, then the high voltage switch logic module routes voltage from the at least one control pad to the at least one memory. The predefined level may be higher than Vdd. Alternatively, the predefined level may be higher than the power supply voltage level of the controller.
In accordance with an embodiment of the present invention the high voltage switch logic module is adapted to direct a portion of the voltage input to the at least one control pad to the controller. The portion of the voltage may comprise Vdd or may be at a level of the power supply of the controller, for example.
There is also provided in accordance with an embodiment of the present invention a method comprising determining if a voltage input to a control pad of a flash memory card exceeds a predefined level, the flash memory card comprising a controller and at least one memory, and routing voltage from the control pad to the controller if the voltage input does not exceed the predefined level.